Enhanced synthesis of C2+ alcohols from syngas over a Co-Co2C catalyst supported on mesoporous carbon–silica composites

Abstract

Higher alcohol synthesis (HAS) from syngas is a promising route for converting non-petroleum fossil energy resources into useful fuels or chemicals, while the design and preparation of highly efficient catalysts remain challenging. Herein, a series of Co0-Co2C catalysts supported on mesoporous carbon–silica composites were prepared for HAS. The composites were derived from carbon-silica nanocages, consisting of uniformly distributed carbon and silica species, which significantly affected the particle dispersion, phase evolution and catalytic performance. With increasing the carbon content, the initial carburization of cobalt was promoted, and some obtained Co2C tended to convert to hexagonal closest packed cobalt (hcp-Co, a highly active site for Fischer-Tropsch), boosting the CO dissociation and catalyst activity. While as the silica content increased, more Co2C phases can be stabilized, leading to enhanced Co2C/Co0 ratio and ROH selectivity. As a result, the optimal 15Co/22Si@C catalyst achieved a ROH selectivity of 40.1% where 96.0 wt% was higher alcohols (HA), and a space time yield (STY) towards HA of 26.5 mmol·gcat−1·h−1, which remarkably outperformed most of the reported Co-based catalysts in HAS. Moreover, the superior stability of over 250 h reaction was obtained, owing to the confinement effect and strong metal-support interaction provided by the mesoporous carbon–silica composites. This work may provide guidance for designing high-performance monometallic cobalt catalyst in HAS.